At least three separate security cameras captured the vicious incident and the hunt led to 19-year-old Stefan Sylvestre -- who they found with acid burns on his hands.

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Sylvestre eventually told authorities he'd been commissioned to throw the acid at Piper by Danny Lynch -- a man Piper had started dating just two weeks before the attack.

Lynch was a 33-year-old martial arts enthusiast who likely first saw Piper when she was working at martial arts matches as a ring girl. Piper said they initially met online.

"The first initial contact was on Facebook, where he messaged me...his profile picture was him in a martial arts outfit. And then, the next few days we carried on, talking online, and eventually swapped numbers," she said. "I really sort of quite fancied him, and the whole image he portrayed to me I really liked."

A night out led to another and the relationship moved very quickly. "One minute, you know, she's single, the next minute she's met this guy. And, you know, that's the first I heard about Danny," said Piper's best friend Kay Little.

"It was an intense relationship in that he was very affectionate, and...whenever I wasn't with him...he was calling me or texting me or e-mailing me and wanted to see me," Piper said.

But one night, Piper learned just how terrifying her new boyfriend was.

"I remember thinking about my mom and dad and all my friends, thinking I'm never gonna see them again," she recalled about the tormenting incident with Lynch. "I genuinely didn't think I would live… he was just unhinged, unstable, and extremely violent."

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After a frightening incident, Lynch made Piper promise to keep what had happened between them a secret. Scared for her life, she agreed.

Piper on Lynch: 'He Was Very Jekyll-and-Hyde'

Afraid to go to the police, Piper returned to her apartment and called Little.

"I mean, she was petrified. She was so scared and ...it was almost like she was in a whirlwind of not knowing what to do because he had been so violent and he had threatened to kill her if, if she sort of brought it up with anyone," Little said.

Traumatized, Piper stayed in her apartment for a few days, but was bombarded by Lynch with messages.

"He was very Jekyll-and-Hyde. He was so emotionally unstable," she said. "He would be, 'I love you,' and this is how strange he was, you know, 'have -- have I ruined things between us?'"

After three days of harassment, Katie finally agreed to go to a local Internet cafe to read a message Lynch had posted on her Facebook page.